A widely used procedure for the determination of antibody to rubella virus in human serum is the hemagglutination inhibition test (HAI). The approved standard rubella hemagglutination inhibition test is described in APPROVED STANDARD: ASM-5, National Committee for Clinical Laboratory Standards, Villanova, Pa. 19085 (1979). The test is based on the principle that agglutination of chick erythrocytes by rubella antigen can be inhibited by antibodies specific for the antigen. A commercially available HAI test is the Rubesure.RTM. Test (Calbiochem-Behring Corp., La Jolla, Calif.) which operates on the same principle but utilizes human erythrocytes. Antibody titers measured by the Rubesure.RTM. test are approximately 2-fold greater than titers measured by the standard HAI test, the difference being due to the species of erythrocyte employed. Although HAI tests are extremely reliable and exhibit excellent sensitivity, they are very time consuming, i.e., the tests require extensive pretreatment of the test sera and involve at least one fairly lengthy incubation so that in most laboratories such tests are performed over two days.
Another type of procedure for the determination of antibody to rubella virus in human serum is the indirect or passive hemagglutination test (PHA). A commercially available PHA test is the Rubacell.RTM. Diagnostic Test (Abbott Laboratories, Chicago, Ill.). The test is based on the agglutination of stabilized human erythrocytes coated with rubella virus soluble antigen in the presence of antibody to the rubella virus. While the Abbott PHA test exhibits comparable sensitivity to HAI tests, it is much less time consuming than HAI tests since it does not require pretreatment of test sera. Final test results with the Abbott test may be obtained approximately 2 hours after test fluid collection.